# ---------------------------------------------------------------------------
#
# This script generates the guides. It can be invoked via the
# guides:generate rake task within the guides directory.
#
# Guides are taken from the source directory, and the resulting HTML goes into the
# output directory. Assets are stored under files, and copied to output/files as
# part of the generation process.
#
# Some arguments may be passed via environment variables:
#
#   WARNINGS
#     If you are writing a guide, please work always with WARNINGS=1. Users can
#     generate the guides, and thus this flag is off by default.
#
#     Internal links (anchors) are checked. If a reference is broken levenshtein
#     distance is used to suggest an existing one. This is useful since IDs are
#     generated by Markdown from headers and thus edits alter them.
#
#     Also detects duplicated IDs. They happen if there are headers with the same
#     text. Please do resolve them, if any, so guides are valid XHTML.
#
#   ALL
#    Set to "1" to force the generation of all guides.
#
#   ONLY
#     Use ONLY if you want to generate only one or a set of guides. Prefixes are
#     enough:
#
#       # generates only association_basics.html
#       ONLY=assoc rake guides:generate
#
#     Separate many using commas:
#
#       # generates only association_basics.html and command_line.html
#       ONLY=assoc,command rake guides:generate
#
#     Note that if you are working on a guide generation will by default process
#     only that one, so ONLY is rarely used nowadays.
#
#   GUIDES_LANGUAGE
#     Use GUIDES_LANGUAGE when you want to generate translated guides in
#     <tt>source/<GUIDES_LANGUAGE></tt> folder (such as <tt>source/es</tt>).
#     Ignore it when generating English guides.
#
#   EDGE
#     Set to "1" to indicate generated guides should be marked as edge. This
#     inserts a badge and changes the preamble of the home page.
#
# ---------------------------------------------------------------------------

require "set"
require "fileutils"

require "active_support/core_ext/string/output_safety"
require "active_support/core_ext/object/blank"
require "action_controller"
require "action_view"

require "rails_guides/markdown"
require "rails_guides/indexer"
require "rails_guides/helpers"
require "rails_guides/levenshtein"

module RailsGuides
  class Generator
    attr_reader :guides_dir, :source_dir, :output_dir, :edge, :warnings, :all

    GUIDES_RE = /\.(?:erb|md)\z/

    def initialize(output=nil)
      set_flags_from_environment

      if kindle?
        check_for_kindlegen
        register_kindle_mime_types
      end

      initialize_dirs(output)
      create_output_dir_if_needed
    end

    def set_flags_from_environment
      @edge     = ENV["EDGE"]     == "1"
      @warnings = ENV["WARNINGS"] == "1"
      @all      = ENV["ALL"]      == "1"
      @kindle   = ENV["KINDLE"]   == "1"
      @version  = ENV["RAILS_VERSION"] || "local"
      @lang     = ENV["GUIDES_LANGUAGE"]
    end

    def register_kindle_mime_types
      Mime::Type.register_alias("application/xml", :opf, %w(opf))
      Mime::Type.register_alias("application/xml", :ncx, %w(ncx))
    end

    def generate
      generate_guides
      copy_assets
      generate_mobi if kindle?
    end

    private

      def kindle?
        @kindle
      end

      def check_for_kindlegen
        if `which kindlegen`.blank?
          raise "Can't create a kindle version without `kindlegen`."
        end
      end

      def generate_mobi
        require "rails_guides/kindle"
        out = "#{output_dir}/kindlegen.out"
        Kindle.generate(output_dir, mobi, out)
        puts "(kindlegen log at #{out})."
      end

      def mobi
        "ruby_on_rails_guides_#@version%s.mobi" % (@lang.present? ? ".#@lang" : "")
      end

      def initialize_dirs(output)
        @guides_dir = File.join(File.dirname(__FILE__), "..")
        @source_dir = "#@guides_dir/source/#@lang"
        @output_dir = if output
          output
        elsif kindle?
          "#@guides_dir/output/kindle/#@lang"
        else
          "#@guides_dir/output/#@lang"
        end.sub(%r</$>, "")
      end

      def create_output_dir_if_needed
        FileUtils.mkdir_p(output_dir)
      end

      def generate_guides
        guides_to_generate.each do |guide|
          output_file = output_file_for(guide)
          generate_guide(guide, output_file) if generate?(guide, output_file)
        end
      end

      def guides_to_generate
        guides = Dir.entries(source_dir).grep(GUIDES_RE)

        if kindle?
          Dir.entries("#{source_dir}/kindle").grep(GUIDES_RE).map do |entry|
            next if entry == "KINDLE.md"
            guides << "kindle/#{entry}"
          end
        end

        ENV.key?("ONLY") ? select_only(guides) : guides
      end

      def select_only(guides)
        prefixes = ENV["ONLY"].split(",").map(&:strip)
        guides.select do |guide|
          guide.start_with?("kindle".freeze, *prefixes)
        end
      end

      def copy_assets
        FileUtils.cp_r(Dir.glob("#{guides_dir}/assets/*"), output_dir)
      end

      def output_file_for(guide)
        if guide.end_with?(".md")
          guide.sub(/md\z/, "html")
        else
          guide.sub(/\.erb\z/, "")
        end
      end

      def output_path_for(output_file)
        File.join(output_dir, File.basename(output_file))
      end

      def generate?(source_file, output_file)
        fin  = File.join(source_dir, source_file)
        fout = output_path_for(output_file)
        all || !File.exist?(fout) || File.mtime(fout) < File.mtime(fin)
      end

      def generate_guide(guide, output_file)
        output_path = output_path_for(output_file)
        puts "Generating #{guide} as #{output_file}"
        layout = kindle? ? "kindle/layout" : "layout"

        File.open(output_path, "w") do |f|
          view = ActionView::Base.new(source_dir, edge: @edge, version: @version, mobi: "kindle/#{mobi}", lang: @lang)
          view.extend(Helpers)

          if guide =~ /\.(\w+)\.erb$/
            # Generate the special pages like the home.
            # Passing a template handler in the template name is deprecated. So pass the file name without the extension.
            result = view.render(layout: layout, formats: [$1], file: $`)
          else
            body = File.read(File.join(source_dir, guide))
            result = RailsGuides::Markdown.new(view, layout).render(body)

            warn_about_broken_links(result) if @warnings
          end

          f.write(result)
        end
      end

      def warn_about_broken_links(html)
        anchors = extract_anchors(html)
        check_fragment_identifiers(html, anchors)
      end

      def extract_anchors(html)
        # Markdown generates headers with IDs computed from titles.
        anchors = Set.new
        html.scan(/<h\d\s+id="([^"]+)/).flatten.each do |anchor|
          if anchors.member?(anchor)
            puts "*** DUPLICATE ID: #{anchor}, please make sure that there're no headings with the same name at the same level."
          else
            anchors << anchor
          end
        end

        # Footnotes.
        anchors += Set.new(html.scan(/<p\s+class="footnote"\s+id="([^"]+)/).flatten)
        anchors += Set.new(html.scan(/<sup\s+class="footnote"\s+id="([^"]+)/).flatten)
        return anchors
      end

      def check_fragment_identifiers(html, anchors)
        html.scan(/<a\s+href="#([^"]+)/).flatten.each do |fragment_identifier|
          next if fragment_identifier == "mainCol" # in layout, jumps to some DIV
          unless anchors.member?(fragment_identifier)
            guess = anchors.min { |a, b|
              Levenshtein.distance(fragment_identifier, a) <=> Levenshtein.distance(fragment_identifier, b)
            }
            puts "*** BROKEN LINK: ##{fragment_identifier}, perhaps you meant ##{guess}."
          end
        end
      end
  end
end
